JPH02115319A - Production of high magnetic flux density grain-oriented silicon steel sheet - Google Patents

Abstract

PURPOSE:To stably produce the title high magnetic flux density grain-oriented silicon steel sheet by holding the steel sheet at a fixed temp. for a specified time in the finish annealing, and heating the sheet at a specified rate to apply purification annealing. CONSTITUTION:A silicon-steel slab contg., by weight, 0.02-0.12% C, 2.5-4.0% Si, 0.03-0.15% Mn, 0.01-0.05% Sol.Al, 0.01-0.20% Sb, 0.004-0.01% M, 0.01-0.05% (S+Se) where <0.01% S, at least one kind among 0.02-0.20% Cu, 0.02-0.20% Sn, and 0.005-0.05% Mo, and the balance Fe is hot-rolled. The hot-rolled sheet is annealed, and then quenched. One or two cold rollings including process annealing are applied at the final draft of >=80%. The sheet is then decarburization-annealed, held at 700-840 deg.C for 20-200hr, and purification-annealed at the temp. increasing rate of 5-50 deg.C/hr to stably produce a high magnetic flux density silicon steel sheet.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a method for producing grain-oriented silicon steel sheets having (110) (0011) orientation as the main orientation.

(Conventional technology) AIN is the main inhibitor, final cold rolling is 80%
Regarding the method of producing grain-oriented silicon steel sheets at the above rolling reduction ratio, many techniques, typified by Japanese Patent Publication No. 15644/1980, have been disclosed. The feature of grain-oriented silicon steel sheets with AIN as the main inhibitor is that they can obtain high magnetic flux density, but on the other hand, because the secondary recrystallized grain size is large, eddy current loss is high and low iron loss is obtained. Moreover, there was a drawback that secondary recrystallization was not stable and the magnetic flux density varied widely.

Among these drawbacks, methods for reducing eddy current loss include the method of irradiating a steel plate with a laser beam as disclosed in Japanese Patent Publication No. 57-2252, or the method disclosed in Japanese Patent Publication No. 61-3939.
This problem is being solved by techniques of artificially subdividing magnetic domains, such as the method of forming regions with different coefficients of thermal expansion, as disclosed in Japanese Patent No. 5.

These methods subdivide the magnetic domains to reduce eddy current loss, and the iron loss reduction effect becomes greater when a high magnetic flux density product plate with low hysteresis loss is irradiated with a laser, plasma jet, etc.

Therefore, technology for stably manufacturing products with high magnetic flux density and low hysteresis loss is becoming important.

By the way, secondary recrystallization is difficult to control because it is a so-called stochastic phenomenon that varies even if it is manufactured under the same conditions.
Particularly in the case of a thin plate with a thickness of 0.23 mm or less, inhibitors such as AIN are likely to decompose during final annealing, making its suppressing power unstable, and therefore secondary recrystallization becomes even more unstable.

Here, as a technique for stabilizing secondary recrystallization, Japanese Patent Publication No. 57-9419 and Japanese Patent Application Laid-open No. 58-217630 disclose a method of adding Sn and/or Cu, and Japanese Patent Publication No. 61-157632 discloses a method of adding Sn and/or Cu. The publication discloses methods for adding sb and Cu, respectively.

However, these methods stabilize secondary recrystallization by adding auxiliary inhibitors such as Sn, Cu, and sb to refine the secondary recrystallized grains. As the diameter became smaller, the magnetic flux density tended to decrease.

(Problems to be Solved by the Invention) An object of the present invention is to propose a method for producing a grain-oriented silicon steel sheet with a high magnetic flux density at a high yield by stabilizing secondary recrystallization.

(Means for Solving the Problems) The inventors have determined that the orientation of secondary recrystallized grains is ideal (110) for producing grain-oriented silicon steel sheets using AIN and MnSe and/or MnS and sb as inhibitors. (00
1) We conducted various studies on the manufacturing conditions in order to get the direction closer to the direction of the high magnetic flux density. It was discovered that silicon steel sheets can be stably obtained.

This invention is derived from the above knowledge.

That is, in this invention, C: 0.02 to 0.12 wt%
, Si: 2.5-4. Owt%, Mn: 0.
03-0.15 wt%, sol.

Eight I: 0.01 to 0.05-t%, Sb
: 0.01 to 0.20 at% and N:
Contains 0.004 to 0.01 wt%, S and/or S
A silicon steel slab containing a total of 0.01 to 0.05 wt% of e, with the balance consisting of iron and unavoidable impurities is hot rolled, hot rolled sheet annealed and rapidly cooled, and then once or intermediately Two times of cold rolling with annealing at a final rolling rate of 8
In a method for manufacturing a grain-oriented silicon steel sheet, which consists of a series of steps of applying 0% or more, followed by decarburization annealing and finish annealing, the finish annealing is performed at a temperature range of 700 to 840°C for 20 hours or more and 200 hours or less. After holding, 5-50″c/
A method for producing a high magnetic flux density grain-oriented silicon steel sheet (first invention), characterized by heating to the temperature range of purifying annealing at a heating rate of h, and then performing purifying annealing (first invention), and C: 0.02 to 0. .12 wt%, St: 2.5
~4. Owt%, Mn: 0.03-0.15 wt
%, sol, At: 0.01-0.05-t%,
Sb: 0.01-0.20wt% and N: 0
．． 004 to 0.01 wt%, and further contains S and/
or Se in a total of 0.01 to 0.05 wt% and C
u: 0.02-0.20-t%, Sn: 0.0
2-0.20wt% and Mo: 0.005-0.
The first method uses a silicon steel slab containing 0.05 wt% of at least one kind, with the remainder consisting of iron and unavoidable impurities.
This is a method for manufacturing a high magnetic flux density grain-oriented silicon steel sheet (second invention) comprising the same steps as the invention.

Now, in the primary recrystallized structure of a grain-oriented silicon steel sheet that has been subjected to the final cold rolling at a rolling reduction ratio of 80% or more, (110) (001) oriented grains form aggregates, which can become the nuclei of secondary recrystallized grains. They often exist alone without being formed, and their number is small, so secondary recrystallization is unstable.

Here, as a method to stabilize secondary recrystallization,
Publication No. 26493 describes cold rolling at a material temperature of 50 to 30.
0°C, and Japanese Patent Publication No. 54-29182 discloses a technology that requires treatment during rolling, such as maintaining the temperature in a range of 300 to 600"C between cold rolling baths. Increasing the temperature of the material during cold rolling improves (110) (001) in the -order crystal structure.
) The aim is to stabilize secondary recrystallization and improve magnetic properties by increasing the number of oriented grains, increasing the number of secondary recrystallization nuclei, and making the secondary recrystallization grains finer.

However, this invention is isolated in the primary recrystallized structure (
Because 110) (001) oriented grains are preferentially generated as secondary recrystallization nuclei and then subjected to secondary recrystallization, even though the number of (110) C00L) oriented grains in the -next crystal structure is extremely small, This is a new method that can stably cause secondary recrystallization and increase the magnetic flux density.
This also increases the number of grains that are deviated from the orientation, so the magnetic flux density does not necessarily improve.

In this invention, first, in order to generate nuclei of secondary recrystallized grains, it is necessary to maintain the temperature in a temperature range of 700 to 840°C for 20 hours or more. Naruto MnS at high temperature where the holding temperature exceeds 840℃
or MnSe and sbノ(1tO) (oot
) The ability to suppress the growth of grains other than oriented grains decreases, and when maintained at that temperature, preferential nucleation of (110) (001) oriented grains does not occur and the magnetic properties of the product after final annealing improve. is very small.

Next, as a material component for which the heat treatment of the present invention is effective, it is essential that sb be contained in an amount of 0.01 to 0.20 wt%. In steel that does not contain sb, the inhibitor AIN in the steel is absorbed through the steel plate surface due to the influence of the atmosphere.
As a result of decomposition or coarsening, the suppressing power is lost and the desired result cannot be obtained. It is known that sb concentrates on the surface, and it is presumed that the influence of the atmosphere on AIN disappears due to the sb concentrated on the surface.

Here, as a conventional finish annealing technique, JP-A-50-123
Publication No. 517 discloses that, in the final annealing process of a silicon steel material with MnSe and/or MnS as the main inhibitor, secondary recrystallization is sufficiently developed at a temperature of 800 to 900°C, and further purification is performed at a temperature of 1000°C or higher. It is disclosed that annealing is performed.

On the other hand, this invention relates to the conditions of finish annealing applied to grain-oriented silicon steel sheet material with AIN as the main inhibitor, and for the material with AIN as the inhibitor, the holding temperature range of 700 to 840°C of this invention is applied. In this case, secondary recrystallization does not occur. This point will be explained in more detail below.

Figure 1 shows a decarburized annealed plate of grain-oriented silicon steel containing AIN,
A comparison of the macrostructures of decarburized annealed plates of grain-oriented silicon steel with MnSe and sb as inhibitors is shown when each plate is annealed at 840°C for 50 hours. The same figure (a) shows when AIN is used as an inhibitor, and the same figure (b) shows MnSe and sb
In the case of (0) in the same figure, secondary recrystallization is completely completed, but in the case of (a) in the same figure, no secondary recrystallized grains are observed. As shown in the figure, when AIN is the main inhibitor, AIN
Since the decomposition temperature of AIN is high and the grain growth suppressing effect works up to high temperatures, secondary recrystallization does not start by annealing at 840'C, and when AIN is used as the main inhibitor, annealing at 950'C
An annealing temperature higher than that is required.

That is, in this invention, it is important to maintain the temperature in a temperature range of 700 to 840''C in which secondary recrystallization does not occur, and it is important to maintain the temperature in a temperature range of 700 to 840''C in which secondary recrystallization does not occur.
This technology is different from the technology described in the publication.

Furthermore, the inventors conducted an experiment in which sb was added to solve the problem of stabilizing secondary recrystallization of grain-oriented silicon steel sheets in which AIN is the main inhibitor, especially for products with a thin finished sheet thickness.

That is, mA consisting of the components shown in Table 1 and the balance being iron,
B, C, and D were manufactured under the conditions shown in Table 2, and 20 product plates were each used as magnetic measurement samples.

The results of those magnetic measurements are shown in Table 3, typical macrostructure photographs are shown in Figure 2, and (110) (222) (20
Table 4 shows the results of measuring the specific strength of each surface of 0).

From Table 3, it can be seen that the composition of steel C, in which sb was added to MnSe, provided stable and good magnetic properties.

In addition, in the steel composition containing MnS and sb, the secondary recrystallized grains became fine and the magnetic flux density decreased slightly, but the fluctuation in characteristics decreased. Components A and B, which do not contain sb, do not provide stable and good magnetic properties.

From Table 4, it can be seen that the X-ray inverse strength of the decarburized annealed plate is higher (110), (222), and 200) for steel C with sb added to Se, compared to mA without sb added.
It can be seen that the intensity is decreasing. As the primary recrystallization texture of the decarburized annealed plate, the (110) strength represents the strength of the (110) (001) oriented grains, which are the nuclei of the secondary recrystallized grains.
(222) strength represents (111) (112) oriented grains which promotes the growth of (110) (001) oriented grains;
The 200) strength can be considered to represent the (100) (011) oriented grains inhibiting the growth of the (110) (001) grains. Therefore, when sb is added to MnSe (
This experimental result in which the 222) strength increased (200>strength decreased) can be interpreted to mean that the growth of (110) (001) grains became extremely good, resulting in improved and stabilized properties.

Furthermore, in fiD in which sb is added to S, (222) increases compared to steel B in which sb is not added, although it is not as remarkable as in the case of Se addition. sb improves the texture of decarburized annealed plates1
10) It was found that the effect of improving the growth properties of [001] oriented grains and stably improving properties is particularly remarkable when sb is added to Se.

(for production) Next, the reasons for limiting the constituent elements of this invention will be described.

C: 0.02 to 0.12 wt% If C is less than 0.02 wt%, secondary recrystallization will be poor, while if it exceeds 0.12 wt%, decarburization property and magnetic properties will be reduced. It was made into the range of .02-0.12 wt%.

Si: 2.5 to 4.0 wt% If Si is less than 2.5 wt%, good iron loss cannot be obtained,
On the other hand, if it exceeds 4.0 wt%, the cold rolling property will be significantly deteriorated, so it should be 2.5 to 4. The range was Owt%.

Mn and S and/or Se are MnS and/or MnS
This is a component for forming e.

First, Mn requires at least 0.03 wt% to exert its effect as an inhibitor, while 0.1'
If it exceeds S wt%, the solid solution temperature of MnS and MnSe becomes high, and the solid solution does not occur at normal slab heating temperatures, resulting in deterioration of magnetism.

If S and/or Se exceeds 0.05 wt%, it will be difficult to purify by purification annealing, while if it is less than 0.01 wt%, the amount of inhibitor will be insufficient, so the total amount of S and/or Se will be 0.01 wt%.
~0.05 wt%. However, S is 0.01 wt.
By regulating the magnetic flux density to less than %, the magnetic flux density is further improved.

AI and N are necessary to form AIN, and 81
The content is in the range of 0.01 to 0.05 wt%.

That is, if Al is too small, the magnetic flux density will be low, and if it is too large, secondary recrystallization will become unstable. Furthermore, N is 0.00
If it is less than 4 wt%, the amount of 8IN will be insufficient and 0.012-
If it exceeds t%, blistering will occur in the product, so 0.
The range is 0.004 to 0.012 wt%.

If sb is less than 0.01 wt%, there is no surface concentration effect,
Moreover, if it exceeds 0.20 wt%, problems will occur in decarburization properties and the formation of a surface film, so the content is set at 0.01 to 0.20 wt%.

Furthermore, Cu can be added to further improve the magnetic flux density. If the content of Cu is less than 0.02 wt%, there is no effect, and if it exceeds 0.20 wt%, the pickling properties and brittleness will deteriorate, so the content should be 0.02 to 0.20 wt%.
%. Furthermore, it is advantageous to add Sn to improve iron loss; if the content of Sn is 0.02 wt% without grooves, there is no effect, and if it exceeds 0.20 wt%, the brittleness deteriorates. 02-0.20 wt%.

Furthermore, MO can be contained in order to improve the surface properties. No effect below 0.005wt%, 0.0
If it exceeds 5 wt%, the decarburization performance will deteriorate, so o, oos~
0.05-1%.

Next, the silicon steel slab made of the above-mentioned steel components is heated and then hot rolled. For example, hot-rolled sheets are heated at 900 to 1200°C.
After annealing, the material is rapidly cooled and then cold rolled once or twice with intermediate annealing at a final rolling reduction of 80% or more.

The reason for limiting the final cold rolling ratio to 80% or more is AIN
This is because the primary recrystallized structure for exerting a strong suppressive force cannot be obtained at a reduction rate of less than 80%.

After cold rolling, decarburization annealing is performed, an annealing separator is applied, and final annealing is performed. Finish annealing is carried out at a constant temperature in the temperature range of 700 to 840'C for 20 hours or more and 200 hours or less, and then heated at a temperature increase rate of 5 to 50 °C/h to the purification annealing temperature range, for example 1200 °C. .

The appropriate holding temperature here varies depending on the inhibitor and the texture of the decarburized annealed plate, but below 700"C (1
10) Magnetic properties do not improve because secondary recrystallization nuclei of (001) oriented grains hardly occur.

When the temperature exceeds 840° C., the suppressive power of MnS and/or MnSe is lost, grains other than (110) (001) oriented grains also undergo normal grain growth, and secondary recrystallization becomes defective. Therefore, the holding temperature is limited to 700 to 840°C.

In addition, the retention time is (110) (001
) The generation time of secondary recrystallization nuclei of oriented grains is short, and magnetic properties do not improve. Over 200 hours, MnS, MnSe,
Secondary recrystallization becomes defective because the suppressing power of AIN decreases.

Therefore, the holding time is limited to 20 to 200 hours.

Temperature increase rate after holding constant temperature is less than 5℃/h and 50℃
If the temperature exceeds c/h, the magnetic flux density decreases, so the temperature should be 5 to 50℃/
h. Purification annealing is performed in hydrogen for example at 1200
'C is carried out for 5 hours to purify S, Se, etc.

In addition, for components containing sb in AIN, final annealing was performed at 7
The reason why the magnetic properties are improved by holding the temperature at a constant temperature in the range of 00 to 840°C for 20 to 200 hours and then increasing the temperature at 5 to 50°C/h is presumed as follows.

M in the production of grain-oriented silicon steel sheets in which AIN is the main inhibitor and the final cold rolling is performed at a reduction rate of 80% or more.
The role of nS or auxiliary inhibitors such as MnSe or sb is still unclear. The temperature at which the suppressing effect is lost during final annealing of AIN, MnS or MnSe is AIN
is 950-1000℃, MnS or MnSe is 800~
950° C., and therefore MnS or MnSe loses its suppressive power in the first half of final annealing. The secondary recrystallization temperature in the production of grain-oriented silicon steel sheets in which AIN is the main inhibitor and the final cold rolling is performed at a reduction rate of 80% or more is 950-1
000° C., and since MnS or MnSe loses its suppressive force in this temperature range, MnSe or MnS does not contribute to reinforcing the suppressive force of AIN during secondary recrystallization. 700
By holding the steel plate in the temperature range of ~840°C for 20 to 200 hours, ^IN usually decomposes or becomes coarse depending on the nitrogen potential of the atmosphere via the steel plate surface, and loses its suppressive power. However, when sb is contained in steel, the sb concentrated on the surface maintains a suppressive force while eliminating the influence of the atmosphere, and nucleates grains in the (110) (001) orientation preferentially, resulting in AIN. It is thought that secondary recrystallization in the (110) [001:1 orientation with excellent orientation is promoted by growing the crystals to a size that can become secondary recrystallization nuclei before reaching the temperature range where the suppressing power is exerted. That is, the fact that such a high magnetic flux density can be obtained through final annealing is a unique phenomenon in steels containing sb in a composition system in which AIN is used as a main inhibitor, MnSe or MnS is used as an auxiliary inhibitor.

(Example) C: 0.062 wt%, Si: 3.10 w
t%, Mn: 0.075wt%, Se:
0.024 wt%, sol, AI: 0.02
5 wt% N: 0.0086 wt%, Sb:
A silicon steel slab consisting of 0.029wt% balance Fe was heated to 1420'C for 20 minutes and then hot rolled to 2.3m.
It was made into a hot-rolled plate with a thickness of m. This hot-rolled sheet was heated at 1050° C. for 2 minutes, then rapidly cooled by mist injection, and then cold-rolled to a thickness of 0.30 mm.

After cold rolling, decarburization annealing was performed at 840° C. for 4 minutes, which also served as recrystallization, and then MgO was applied and finish annealing was performed. The magnetic properties of the product board thus obtained are shown in Table 5. The conditions for cold rolling and final annealing are as follows.

(i) Cold rolling conditions A: Rolling at room temperature B: Rolling at 200'C C: Rolling after holding at 260°C for 130 seconds between passes (ii)
Final annealing condition a: 1200°C at 10°C/h after holding at 800°C for 50 hours
After holding at 50℃ for 10,000 hours, increase the temperature to 120℃ at 10/h.
Temperature raised to 0°C: 120 at 10/h after holding at 650°C for 10,000 hours
Temperature increase to 0℃: 1200℃ at 10℃/h after holding at 900℃ for 50 hours
Temperature raised to 1200°C at 10°C/h after holding at 800°C for 5 hours f: 10/h after holding at 800'C for 24040 hours
Temperature raised to 1200℃ at 1200℃ at 100'c/h after holding at 800℃ for 50 hours
Temperature increase to °C: 1200 at 2.5 °C/h after holding at 800 °C for 50 hours
Temperature increase to °C i: Temperature increase from 800 °C to 1200 °C at 10 °C/h As is clear from the same table, an example conforming to this invention in which the temperature was raised at 10 °C/h after holding at 850 °C for 50 hours during final annealing. In this method, products with high magnetic flux density were stably obtained.

Example 1 A silicon steel slab having the composition shown in Table 6 was prepared.
A product with a thickness of 0.30 mm+ was produced according to the same conditions as above. However, cold rolling is performed at room temperature, and final annealing is performed at 80°C.
After holding at 0°C for 50 hours, the temperature was raised to 1200°C at 0''C/h.

Endorsement 142 Silicon steel slabs with the composition shown in Table 7
After heating at 0'C for 20 minutes, it was hot rolled into a hot rolled sheet with a thickness of 2.01. This hot-rolled sheet was heated at 1050°C for 2 minutes, then rapidly cooled by mist injection, and then heated to 0.23 m
It was cold rolled to a thickness of m. After cold rolling, decarburization annealing was performed at 840°C for 4 minutes, which also served as recrystallization, and then Mgo was applied.
After holding at 50°C for 100 hours, final annealing was performed by heating to 1200°C at a temperature increase rate of 10°C/h. The magnetic properties of the product plate thus obtained are shown in the same table, and good magnetic properties were obtained even with a thin plate thickness of 0.23 mmW.

(Effects of the Invention) According to the present invention, grain-oriented silicon steel sheets with high magnetic flux density can be manufactured by a method of stabilizing secondary recrystallization, and silicon steel sheets with excellent magnetic properties can be manufactured with high yield. .

[Brief explanation of the drawing]

Figures 1 (a) and (0) and Figures 2 (8) to (D) are photographs showing the metal structure. Patent applicant: Kawasaki Steel Co., Ltd.

Claims (1)

[Claims] 1. C: 0.02 to 0.12 wt%, Si: 2.5 to 4.0 wt%, Mn: 0.03 to 0.15 wt% sol. Contains Al: 0.01 to 0.05 wt%, Sb: 0.01 to 0.20 wt%, and N: 0.004 to 0.01 wt%, and further contains S and/or Se in a total of 0.01 to 0.05 wt%. %, with the balance consisting of iron and unavoidable impurities, is hot-rolled, subjected to hot-rolled plate annealing and rapid cooling, and then cold-rolled once or twice with intermediate annealing in between. In a method for manufacturing a grain-oriented silicon steel sheet, which consists of a series of steps of rolling at a rolling rate of 80% or more, followed by decarburization annealing and finish annealing, the finish annealing is carried out at a temperature range of 700 to 840°C for 20 hours or more and 20 hours or less. 1. A method for manufacturing a grain-oriented silicon steel sheet with high magnetic flux density, characterized in that the steel sheet is held at a temperature of 5°C to 50°C/h, then heated to a temperature range for purification annealing at a temperature increase rate of 5 to 50°C/h, and then subjected to purification annealing. 2, C: 0.02-0.12 wt%, Si: 2.5-4.0 wt%, Mn: 0.03-0.15 wt% sol. Contains Al: 0.01 to 0.05 wt%, Sb: 0.01 to 0.20 wt%, and N: 0.004 to 0.01 wt%, and further contains S and/or Se in a total of 0.01 to 0.05 wt%. %and,
Cu: 0.02-0.20wt%, Sn: 0.02-0
．． 20wt% and Mo: 0.005-0.05wt%
A silicon steel slab containing at least one of Rolling is performed at a final rolling ratio of 80% or more,
In a method for producing a grain-oriented silicon steel sheet, which comprises a series of steps of decarburization annealing and finish annealing, the finish annealing is held at a temperature range of 700 to 840°C for 20 hours or more and 200 hours or less, and then A method for producing a high magnetic flux density grain-oriented silicon steel sheet, which comprises heating to a purifying annealing temperature range at a heating rate of 50° C./h, and then performing purifying annealing. 3. The manufacturing method according to claim 1 or 2, wherein the S content is 0.01 wt% or less.